This is a rather extensive list of nature/science museums in Colorado. I include the location for each as they can serve not only as a resource for you as a teacher, but as a way to bring realia into science classrooms, or rather, bring students to the realia. This gives you the opportunity to explore different types and prices of museums to find what may work best for your class.

Name and Link of Museum
Location
Hands-on
Main Topics
Highlights
The John McConnell Math and Science Center -
Grand Junction
yes
very diverse
small, exploratory
The Denver Museum of Nature and Science
http://www.walkingmountains.org/

Denver
no
diverse
huge, thorough
Dinosaur National Monument
Dinosaur
yes
geology, paleontology, nature
out-doors
Dinosaur Ridge
Morrison
yes
geology, paleontology
out-doors
Dinosaur Journey
Fruita
yes
paleontology
animatronic dinos!
Florissant Fossil Beds National Monument
Florissant
yes
paleontology, geology
out-doors
Garden of the Gods Visitor and Nature Center
Colorado Spgs.
yes
geology, nature
out-doors
The Butterfly Pavilion
Westminster
yes
biology, insects
tropical and native insects
Moraine Park Museum and Amphitheater
Estes Park
yes
biology, nature
out-doors
Morrison Natural History Museum
Morrison
yes
paleontology
small, friendly
Rocky Mountain Dinosaur Resource Center
Woodland Park
yes
paleontology
live lab
University of Colorado Museum of Natural History
Boulder
no
rotating, check for current
local focus
Colorado School of Mines Geology Museum
Golden
no
geology, mineralogy
rock ID, moon rock!
Durango Discovery Museum
Durango
yes
diverse, STEM
STEM focus for all ages
Space Foundation Discovery Center
Colorado Spgs.
some
space
applied science
Fort Collins Museum of Discovery
Fort Collins
some
diverse
local and standards aware
The Wildlife Experience Museum
Denver
some
biomes, rotating displays
local focus
Colorado Gators Farm
Mosca (near
Alamosa)
no
biology
alligators!
Downtown Aquarium
Denver
no
biomes, biology, fish
underwater life up close
The Wild Animal Sanctuary
Keensburg (NE
of Denver)
no
large carnivore sanctuary
huge cats
Garbage Garage Education Center
Fort Collins
no
recycling/trash
trash
Colorado Wolf and Wildlife Center
Divide (near
Florissant)
no
biology/wolves
real live wolves
Pueblo Zoo
Pueblo
no
biology
standards directed lessons
CSU Environmental Learning Center
Fort Collins
yes
biology, nature
outdoor lessons
Denver Zoo
Denver
no
biology
active and in person
Walking Mountains Science Center
Avon
yes
biology, nature
hiking, field science
Grand Valley Zoological Quest
Fruita
yes
biology, nature
standards oriented lessons